After having chosen the best configuration with the library [1]}, we carry on with the learning until the early stopping criterion with a patience of 30 epochs is met. The early stopping criterion is based on the improvement in the normalized mean squared error of the UL validation set.
In this section, three different AE framework are considered:
i) “AE”: the AE in [2]} presented in Section ;
ii) “ND”: a modified version of “AE” where the hyperbolic tangent activation function at the encoder output has been replaced by the ND layer as described in Section ;
iii) “VQ-VAE”: a modified version of “AE” where the hyperbolic tangent activation function at the encoder output has been removed and the learning is conduced as described in Section .
